Involved in the biosynthesis of chondroitin and dermatan sulfate. The human chondroitin synthetase is a bifunctional glycosyltransferase, which has the 3-beta-glucuronosyltransferase and 4-beta-N-acetylgalactosaminyltransferase (EC 2.4.1.175) activities required for the synthesis of the chondroitin sulfate disaccharide repeats. Similar chondroitin synthase 'co-polymerases' can be found in Pasteurella multocida and Escherichia coli. There is also another human protein with apparently only the 3-beta-glucuronosyltransferase activity.